Upgrading to the 3.5 Kernel fixes this problem for me - however. I did need to remove the following from:

Code:

acpi_osi=linux acpi_backlight=vendor

from the line:

Code:

GRUB_CMDLINE_LINUX_DEFAULT="quiet"

in

Code:

/etc/default/grub

and re-run

Code:

# update-grub

I'd previously added those additional entries when I was using the 3.4 kernel in an effort to fix the problem. Thought I'd post here in case anyone else upgrades to 3.5 and this still appears broken. That's what happened to me - removing the acpi references and regenerating my grub.cfg solved it for me (after a re-boot of course).

If jiml can confirm this now works for him I think this thread can be marked as solved.

gryphon

slh

Post subject:Posted: 24.07.2012, 13:29

Joined: 2010-08-25
Posts: 919

Status: Offline

Thanks for testing.

"acpi_osi=linux" is usually an error, because even though this would be the right setting in theory, vendors only test the windows specific code paths, therefore linux masquerades itself as windows to ACPI to avoid these untested and usually broken APCI code paths.

jiml

Post subject:Posted: 28.07.2012, 01:45

Joined: 2010-09-22
Posts: 4

Status: Offline

I can can confirm that with kernel 3.5 I can now control the brightness again, thanks guys.